A piston for an internal combustion engine is known, having a piston head, a piston skirt, a pair of pin bosses for supporting a piston pin around a pin axis line as a center, and a pair of side walls extending in a direction orthogonal to the pin axis line in plan view and coupling the pin bosses and the piston skirt. In each of the side walls, a through hole penetrating the side wall in the pin axis line direction is formed (refer to, for example, JP-A No. 2000-337212).
Another piston is also known, in which a pair of coupling walls that couple a pair of side walls coupling pin bosses and a piston skirt are formed in positions sandwiching a pin axis line in a direction orthogonal to the pin axis line in plan view in order to enhance rigidity of a piston for an internal combustion engine (refer to, for example, JP-A No. 2007-309271).